In dental treatment a cord can be used for retracting gingiva from a prepared tooth. This cord is named a retraction cord and is packed between gingival tissue and the margin of the prepared tooth (this region is also called sulcus) using an appropriate dental instrument. This procedure however may be cumbersome and can result in discomfort to the patient and also may cause inaccurate margins for the final restoration.
For a more convenient placement retraction pastes are used. The retraction pastes currently commercially available are based on an aqueous clay suspension of a hemostatic agent such as aluminum chloride (Expasyl by Kerr Corporation, Orange Calif. or Retraction Capsule by 3M Espe Minneapolis Minn.). However these pastes must be rinsed after placement adding another step. Moreover, if insufficient rinsing is done, curing of adhesive placed afterward at the site may be negatively affected.
Gingival retraction systems based on a 2-part addition silicone are also available. One such system is Gingitrac MiniMix by Centrix, Shelton Conn. This material contains an aluminum based astringent. However, after syringing to the site, a foam cap must be used to press the material into the sulcus. This is an additional step to the procedure.
U.S. Pat. No. 5,676,543 describes a moldable material formed over teeth with a second flowable material containing an astringent placed into the impression of the teeth in the moldable material providing retraction and hemostasis at the gum line. A moldable material, preferably a silicone, may contain an astringent such as aluminum ammonium sulfate is made into a mold of teeth. The impression formed in the mold of the teeth is filled with a less viscous or initially flowable material also containing an astringent. The mold with the flowable material is placed over the teeth. The initially flowable material preferably sets into a solid. The flowable material may be made of a condensation silicone having a base and catalyst. The mold helps to apply pressure to the flowable material which is transmitted to the gum tissue resulting in retraction and hemostasis.
U.S. Pat. No. 7,195,483 describes a method and a device for effecting the cordless retraction of the gingival sulcus tissue prior to the taking of an impression of a tooth for making a crown or bridge which is attained by controlling any bleeding in the gingival sulcus area, and utilizing a dental dam preferably formed of a sponge or foam like material to contain an astringent fortified silicone impression material embedded about the prepared tooth, and using the patient's biting force to apply the necessary pressure onto the dam until the silicone impression material sets and adheres to the dam to enhance easy removal of the set impression material from the tooth. The dam is formed to accommodate either the posterior teeth or the anterior teeth. The dam has retainers formed therein for aiding in holding the silicone impression material.
U.S. Pat. No. 8,470,905 describes a method and a device for effecting the cordless retraction of the gingival sulcus tissue that includes a dam shaped to be fitted onto a tooth. In one embodiment, the well of the dam is pre-filled with a predetermined amount of a flowable retraction material having a heavy viscosity or putty consistency. In another embodiment a hydrophilic material is added. The preloaded tooth dam is fitted to a prepared tooth so that when pressure is applied onto the tooth dam, the retraction material is displaced under pressure and forced into the sulcus, causing the gingival tissue to retract away from the tooth to enlarge the gingival sulcus. In another embodiment the cap is filled with a dilatant material. In another embodiment, the cap is filled with an impregnated compressible porous material. In yet another embodiment, the cap is pre-dosed with an astringent or hemostatic agent.
U.S. Pat. No. 7,549,862 describes a process of retraction of sulcus, comprising the steps of: applying a silicone material onto and/or at the vicinity of the boundary of a tooth and adjacent sulcus, which silicone material expands during or after its curing reaction; applying a cap onto said tooth, thereby forming a chamber over said silicone material, wherein said chamber comprises as its walls the tooth, the cap and an outer section of said sulcus; whereby said chamber allows for the silicone material to expand into the crevice between sulcus and tooth. Said cap is at least partially filled with a plastically deformable material when applied onto said tooth in step; and/or said cap is deformable, especially under biting pressure.
There is still a need to achieve good retraction of the gingiva using paste delivery with a convenient reduced step procedure that does not rely on a compression cap or a rinsing step.